Artificial sound channel



April 6, 1965 R. A. ARNOLD! ARTIFICIAL SOUND CHANNEL- Filed Sept. 29, 1960 2 Sheets-Sheet 1 IN l/ENTOR ROBERT A. ARNOLD/ Mfi-WM m 2 v A/ W w. N m T T A April 6, 1965 R. A. ARNOLDI ARTIFICIAL SOUND CHANNEL 2 Sheets-Sheet 2 Filed Sept. 29 1960 MW, H

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United States Patent Cfifice 3,177,466 Patented Apr. 6, 1965 3,177,466 ARTIFICIAL SGUND CHANNEL Robert A. Arnoldi, Elmwood, Conn, assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Sept. 29, 1960, Ser. No. 59,320 18 Claims. (Cl. 340-6) This invention relates to artificial sound channels in water and more particularly to channels which can be utilized for confining signals for underwater detection.

A natural acoustic phenomenon has been observed in the ocean in which a minimum velocity of sound exists at a particular depth. This region of minimum sound velocity is in the form of a substantially horizontal layer having a predetermined thickness or depth and has been defined as the Sofar Layer. This type oflayer has the effect of retracting sound waves so that they remain substantially within the layer provided, of course, that the initial path of the sound waves does not make too great an angle with respect to the plane of the layer. Where such a sound channel exists, it has been determined by experiment that sound waves will travel substantially great distances rather than being refracted and completely dissipated within a few miles, such as is the case of present sonar systems.

It is, therefore, a primary object of this invention to create artificial channels in a body of liquid, such as the ocean, by forming a vertical sheet or curtain which will have different characteristics from the adjacent liquid.

It is a further object of this invention to provide vertical curtains of liquid of different characteristics in which a sound receiver is located so as to detect, either by passive or active devices, any sound that is generated in the curtain. Thus, if an enemy submarine penetrated the curtain, either its own sound, or reflected sound or interrupted sound, can be utilized as a signal to detect the foreign object.

These and other objects of this invention will become readily apparent from the following detailed description of the drawings in which:

FIG. 1 is a pictorial presentation in partial schematic of a sound channel-creating arrangement in any typical body of water;

FIG. 2 is a typical vertical cross section of the curtain and surrounding water of FIG. 1;

FIGS. 3 and 4 are vertical pictorial illustrations showing modified arrangements for producing the sound channel;

FIG. 5 is another modification of the invention for waters of colder climate;

FIG. 6 is a diagrammaticrillustration of sound waves traveling in the curtain and viewed in plan.

Referring to FIG. 1, an elongated performated pipe 10 is illustrated as being held adjacent the bottom of the ocean, or similar body of water, by means of a plurality of anchors 12 and'l t. The pipe 10 is connected to a pump 15 orother suitable air supply device which can receive its supply of air from an internal tank or from the surface by means of a line 16. The air ejected from the perforations 18, bubbles vertically toward the surface of the water as also seen in FIG. 2. As the air bubbles rise, they entrain the relatively colder water at the bottom of the ocean and produce a vertical curtain which may diverge in an upward direction as shown. This vertical curtain will have, due to itstemperature, a characteristic different from the adjacent water 22. This curtain of different liquid characteristics will permit sound waves to travel within the curtain at very long distances much in the same manner as they do in thefsofar Layer. Experiments have shown that excellent sound transmitting and receiving characteristics have been obtained.

Thus as seen in FIGS. 1 and 2, a sound transmitter may be used; and a suitable sound pickup or receiver 34 may also be located within the vertical liquid curtain. A suitable sonar type control 36 may be provided. In this arrangement a reflective detection device is utilized. Thus the transmitter 30 transmits sound waves of suitable frequency along the curtain, and in the event there is any foreign object, such as a submarine, penetrating the curtain, reflections therefrom will signal back to the sound receiver 34. It has been found that certain frequencies of sound aimed in certain directions can be made to follow certain patterns. These can readily be used for any form of sound detection to provide a large amount of data or necessary information as to location, speed, and

direction of a foreign object penetrating the curtain.

Thus, as shown in FIG. 6, transmitter 40 may be utilized to produce a sound source which emits sound waves of frequency A and frequency B at relatively large and small angles, respectively, in relation to the plane of the sound curtain. Various determinations can be made by the interruptions of these sound waves by any submarine. Thus, the target size can be determined when the length of time the sound waves of frequency A or frequency B show or reflect an interference from a target. Of course, the speed of the target will also have to be determined. The speed of the target can be determined readily by observing or recording the lapse of time between the beginning of an interference of the sound waves of frequency A and the beginning of an interference of the sound waves of frequency B since the amplitude of each would be known.

By determining the phase of sound waves A relative to sound waves B at the point of interference (interruption), the target range is readily ascertainable. Of course, the range at the point of entrance to the sound channel or curtain and the range at the point of leaving will obviously provide the course or direction of travel of the particular target. Any number of electronic devices for computing these variousdeterminations may be utilized, a number of which are well known in the sonar art.

FIG. 3 illustrates a typical arrangement whereby a surface vessel may pass along a predetermined path and drop a number of bottles 50 of compressed gas such that a line of bubbles will b eemitted so as to entrain water of different temperature from the bottom of the liquid body toward the top or the surface of the liquid. With such an arrangement, a destroyer type vessel may drop any pattern of curtain and then utilize its own sonar detection device or that of an accompanying helicopter to detect the presence of enemy submarines.

Likewise, as seen in FIG. 4, chemical pellets 54 may be utilized which can slowly dissolve and descend to the bottom so that a curtain of liquid having different physical or chemical properties can be formed. Thus, there may be other means of providing different properties to the curtain of water since it has been observed that even the salinity difierence of a liquid will vary the speed at which sound travels within that liquid.

As shown in FIG. 5, during winter conditions where the upper levels of the water are colder than the lowe levels, it may be necessary to provide a pair of curtains 60 and 62 which will entrain warmer water from the bottom so as to form therebetween a curtain 66 of cold water, along which curtain sound may be transmitted at relatively long the bubbles may cause a deterioration of the sound transmission and/ or reception. It has been shown by experiment that once a curtain has been established in this manner in a relatively calm body of water, it will last for several hours.

It will be apparent that the basic principles involved in this invention are equally applicable to the detection of sound in an underwater communications system.

As a result of this invention, it will be apparent that a very simple, efiicient, and highly reliable means has been provided for creating an artificial sound channel in large bodies of water whereby long range sound transmission, and foreign body detection can be provided.

Although several embodiments of this invention have been described herein, it will be apparent that various changes can be made in the arrangement and construction of the various parts without departing from the scope of this novel concept.

I claim:

1. An underwater detection system comprising means for creating a curtain of Water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction parallel to the Water surface for a predetermined distance, said curtain having a predetermined thickness pattern, said curtain being capable of conducting wave energy a substantial distance which energy is confined within the curtain by the characteristic differences of the adjacent water, and sound receiver means in said curtain.

2. A system according to claim 1 wherein said different characteristics are different temperatures.

3. A system according to claim 1 in which said wave energy comprises sound waves.

4. A system according to claim 1 including means for generating wave energy within said curtain.

5. An underwater detection system comprising means for creating a curtain of water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction substantially parallel to the water surface for a predetermined distance, means for transmitting wave energy which travels within said curtain a substantial distance and is confined within the curtain by the characteristic differences of the adjacent water, and means at a predetermined distance from said transmitting means and located within the plane of said curtain for receiving said wave energ 6. A detection system according to claim 5 in which said different characteristics are a difference in temperature.

7. A detection system according to claim 5 in which said wave energy comprises sound waves.

8. A detection system according to claim 5 in which said different characteristics are differences in salinity.

9. A detection system according to claim 5 in which said transmitting means and receiving means comprise a passive detection system.

10. An underwater detection system comprising means for creating a curtain of water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction parallel to the water surface for a predetermined distance, said curtain having a predetermined thickness pattern, said curtain being capable of conducting wave energy a substantial distance which energy is confined within the curtain by the characteristic differences of the adjacent water, means for generating wave energy in said curtain, and means located within said curtain for receiving wave energy generated within the curtain.

11. A system according to claim wherein said different characteristics are difierent temperatures.

12. A system according to claim 10 in which said wave energy comprises sound waves.

13. A system according to claim 10 wherein said characteristics are differences in chemical properties.

14. An underwater detection system comprising means for creating a vertical curtain of water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction substantially parallel to the Water surface for a predetermined distance including a submerged elongated pipe for discharging a fiuid along its length and which fluid travels toward the water surface, means adjacent one end of said curtain for transmitting wave energy which travels within said curtain a substanial distance and is confined within the curtain by the characteristic differences of the adjacent water, and means at a predetermined distance from said transmitting means and located substantially within the plane-0f said curtain for receiving said wave energy.

15. An underwater detection system comprising means for creating a vertical curtain of water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction parallel to the water surface for predetermined distance, means adjacent one end of said curtain for transmitting sound waves which travel within said curtain a substantial distance and are confined within the curtain by the characteristic differences of the adjacent water, and sound receiver means at a predetermined distance from said transmitting means and located Within the plane of said curtain for receiving said sound waves.

16. An underwater detection system comprising means for creating a vertical curtain of water having different characteristics than the surrounding water, said curtain extending from a predetermined depth to the surface and extending in a direction parallel to the water surface for a predetermined distance including an elongated pipe submerged in the water, said pipe being perforated along a predetermined length thereof, a source of fluid under pressure connected to said pipe and being less dense than the surrounding water, means for controlling the flow of said fluid whereby it rises to the surface from said pipe to form said curtain, means adjacent one end of said curtain for transmitting sound waves Which travel Within said curtain a substantial distance and are confined Within the curtain by the characteristic difi'erences of the adjacent water, and sound receiver means at a predetermined distance from said transmitting means and located within the plane of said curtain for receiving said sound waves.

17. A detection system according to claim 16 wherein said fluid is a gas which rises from the pipe and entrains water of low temperature such that said curtain is formed of water having a lower temperature than the adjacent water.

18. An underwater detection system comprising means for creating a main curtain of water having different characteristics than the surrounding water, including a pair of spaced apart devices for creating a vertically rising pair of auxiliary curtains having a relatively higher temperature than the main curtain located between said auxiliary curtains, said curtain extending from a predetermined depth to the surface and extending in a direction parallel to the water surface for a predetermined distance, said curtain having a predetermined thickness pattern, said curtain being capable of conducting wave energy a substantial distance which energy is confined within the curtain by the characteristic differences of the adjacent water, and means located Within said curtain for eceiving wave energy generated within the curtain.

No references cited.

CHESTER L. I UST US, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner. 

1. AN UNDERWATER DETECTION SYSTEM COMPRISING MEANS FOR CREATING A CURTAIN OF WATER HAVING DIFFERENT CHARACTERISTICS THAN THE SURROUDING WATER, SAID CURTAIN EXTENDING FROM A PREDETERMINED DEPTH TO THE SURFACE AND EXTENDING IN A DIRECTION PARALLEL TO THE WATER SURFACE FOR A PREDETERMINED DISTANCE, SAID CURTAIN HAVING A PREDETERMINED THICKNESS PATTERN, SAID CURTAIN BEING CAPABLE OF CONDUCTING WAVE ENERGY A SUBSTANTIAL DISTANCE WHICH ENERGY IS CONFINED WITHIN THE CURTAIN BY THE CHARACTERISTIC DIFFERENCES OF THE ADJACENT WATER, AND SOUND RECEIVER MEANS IN SAID CURTAIN. 